Research into the safety and efficiency of underground placer mining and frozen ground

Some of the underground excavation problems encountered in arctic and subarctic environments associated with thermal disturbance are excessive settlement of ground surface and pronounced displacement around openings. This study investigated the possible links between the significant settlement. Ground temperature was found to be the most influential. An empirical equation was developed for the USBM gravel room to predict the effect of temperature on creep of frozen gravel. Separation of the roof gravel and silt was observed as steady heating process increased the gravel temperature by one degree. The temperature dependent material constants were estimated from the laboratory testings. The factors affecting the creep characteristics were temperature and applied stress level. The primary creep behavior of frozen gravel loaded under 18% of unconfined compressive strength at 25° and 29° could be predicted empirically.U. S. Bureau of Mines, Fairbanks Office, Fairbanks, Alaska; Office of Surface Mining, Division of Technical Services and Research, Washington, D. C.Abstract -- Acknowledgement -- Table of contents -- List of figures -- List of tables -- I. Introduction -- II. USA CREEL permafrost tunnel -- History -- Tunnel geology -- Silt -- Gravel -- Bedrock -- Ground ice -- III. Field instrumentation and monitoring -- Instrumentation -- Monitoring -- Air temperature -- Ground temperature -- Creep deformation -- Strata separation -- IV. Laboratory creep tests -- Theory -- Creep -- Strength -- Cold laboratory facility -- Specimen preparation -- Testing procedures and results -- V. Conclusions -- References -- Appendices

Land application of sewage effluent for Missouri water resources conservation and pollution control

The overall objectives of this study are twofold: 1) to demonstrate the viability and effectiveness of land treatment system to renovate lagoon effluent quality in Missouri and elsewhere in the Midwest; and 2) to conduct a comprehensive and systematic study to develop pertinent design and operating parameters that can be successfully used by other communities in the region. The report described herein represents the results that is necesssary before further development can be initiated. These results are: 1) community background survey; 2) current and proposed waste management methods; and 3) existing surface and subsurface water qualities at application site. Emphasis of the discussion is placed on the technical data which have a direct bearing on the future evaluation of the water quality improvement as a result of land application.Project # G-852 Agreement # 14-08-000

An Opening Profile Recognition Method for Magnetic Flux Leakage Signals of Defect

The defect opening profile recognition is of great concern in the magnetic flux leakage (MFL) measurement technique. The detected spatial MFL signal has three components: horizontal, vertical, and normal components. Horizontal and normal component signals are commonly used to estimate the defect profile, while the vertical component has always been neglected. With the development of the high resolution and the 3-D MFL testing techniques, the vertical component signal is becoming more available. This paper analyzes the essential right-angle features of the vertical component signal, which is useful for the defect opening profile recognition. After obtaining the initial profile from the horizontal or normal component, the types of the right angle is identified from the vertical component, and the opening profile is further optimized based on these right-angle features. The opening profile recognition method is put forward in this paper to improve the accuracy of the recognition result of the defect. Both simulation and experimental tests are conducted to verify the good performance of the proposed method. Compared with the opening profiles recognized merely by the horizontal component signal, the proposed method shows better recognition results, which also validates that the vertical component signal can also be a useful information for the defect estimation

Electromagnetic ultrasonic guided wave long-term monitoring and data difference adaptive extraction method for buried oil-gas pipelines

An increasing number of buried oil-gas pipelines are generated in recent years and defects occur with higher probability in their long-running process. This work proposes an electromagnetic ultrasonic guided wave (EUGW) long-term monitoring scheme for buried oil-gas pipelines and a data difference adaptive extraction method for the monitoring data. The T (0,1) mode guided wave is selected because of its non-dispersive characteristic. For the electromagnetic acoustic transducer (EMAT), a circumferentially magnetized nickel strap is bonded on the pipe to provide the bias magnetic field and the excitation coils are winded on the nickel strap to provide the dynamic magnetic field. A detection stub is planted on the ground and the connector of buried coils is installed in the stub. The difference array is constructed and adaptive gain and attenuation are performed in the data difference adaptive extraction method. The EUGW long-term monitoring scheme is on-site applied for buried oil pipes in Jinan city, Shandong province, China. The EMAT is installed and buried with the pipe, and the periodical detection is conducted from December 2015 till now, once per month. A pit is found and verified by excavation at the distance 9.25 m from the buried EMAT on the flow direction. On-site detection results show that the data extraction method can dramatically improve the signal to noise ratio of the monitoring data and accurately extract the difference and variation of the pipe's structural health condition that occurred in the long-term service. The EUGW long-term monitoring scheme is proved to be a feasible method with prosperous prospect for the structural health monitoring of buried oil-gas pipelines

Investigating the quality inspection process of offshore wind turbine blades using B-spline surfaces

Wind turbines can only extract their rated amount of power if their blades conform closely to the Computer Aided Geometric Design (CAGD). This is quantified by reconstructing B-spline surfaces from measurement data taken from the blade. For reliable comparisons between the surface and CAGD, the generated surface must be an accurate representation of the part. To do this, the input parameters to the fitting process need to be optimized. Previously this has proved to be time consuming and computer intensive. This paper has focused on presenting a protocol for control point locations that increases the initial surface fitness; therefore, decreasing the time taken for an optimiser to converge on the ideal locations. The presented protocol was found to increase the fitness of a surface by up to 150%. For low tolerance products it has been observed that the protocol could remove the need for an optimiser all together

Fast quasi-synchronous harmonic algorithm based on weight window function- mixed radix FFT

According to the requirements of IEC61850-9-2LE, digital energy metering devices mainly adopt 80×fr fixed sampling rate. When the harmonic analysis is carried out under asynchronous sampling, it will produce large errors due to spectral leakage. Quasi-Synchronous Algorithm has high accuracy, but the calculation process is complicated and the hardware overheads are high. Based on the characteristics of digital energy metering devices, this paper puts forward a Fast Quasi-Synchronous Harmonic Algorithm using weight window function combined with Mixed Radix Fast Fourier Transform Algorithm. It will reduce the calculation by more than 94%. Compared with the Triangle/Hanning/Nuttall4(III)-Windowed Interpolated FFT Algorithm, the proposed algorithm will perform better in accuracy and has the feature that the more asynchronous of the sampling, the more obvious the error will be

Problems in the classic frequency shift islanding detection methods applied to energy storage converters and a coping strategy

This paper first derives a usable formula based on the parallel R, L, C load and the conclusions from frequency shift islanding detection methods in current literature: the angle by which the total output current of the distributed resources (DR) units leads the point of common coupling (PCC) voltage must be conducted to have the same shifting direction as the load admittance angle during the variation of the frequency. On the basis of the formula and multi-DR operation, the scenarios in which the classic frequency shift methods are applied to energy storage converters are analyzed. The results indicate that the setting of the angle by which the energy storage converter current leads the PCC voltage may need to be modified when running state changes. It results in the problems that the classic methods are not applicable for non-UPF (unity power factor) control and have to distinguish between generation mode and consumption mode for UPF control. On account of the problems, a coping strategy, i.e. an improved method, is proposed. The analyses indicate that the improved method is applicable in every state. The last simulations and experiments confirm the preceding conclusions

An irregular current injection islanding detection method based on an improved impedance measurement scheme

One class of islanding detection methods, known as impedance measurement-based methods and voltage change monitoring-based methods, are implemented through injecting irregular currents into the network, for which reason they are defined in this paper as irregular current injection methods. This paper indicates that such methods may be affected by distributed generation (DG) unit cut-in events. Although the network impedance change can still be used as a judgment basis for islanding detection, the general impedance measurement scheme cannot separate island events from DG unit cut-in events in multi-DG operation. In view of this, this paper proposes a new islanding detection method based on an improved impedance measurement scheme, i.e., dynamic impedance measurement, which will not be affected by DG unit cut-in events and can further assist some other equipment in islanding detection. The simulations and experiments verify the stated advantages of the new islanding detection method

Profile imaging of actual defects in steel plate based on electromagnetic ultrasonic SH guided wave scattering

Defects occur almost inevitably during the service life of steel plate structures. Industrial safety requirements for steel plate structures are increasingly stringent and the need for defect imaging is urgent. This work proposes a profile imaging method aimed at actual defects in steel plate based on electromagnetic ultrasonic shear horizontal (SH) guided wave scattering. Firstly, a scattering model is proposed based on the characteristics of wave scattering employing the rectangular coordinate system. Scattering points and scattering edges are defined and calculated after the positions of scattering points are proved to be unique on the condition that the transmitting direction is known. Secondly, detailed procedures of the actual defect profile imaging method are provided, exploiting direction-controllable transmitters and omnidirectional receivers. Thirdly, an experimental platform on a steel plate with an actual defect is set up. Electromagnetic acoustic transducers based on SH guided waves are applied to stimulate and receive SH waves. The proposed profile imaging method and procedures are conducted on the experimental platform and a profile image of the actual defect is obtained. The error between the calculated profile and actual profile is then defined and displayed on the plane of the rectangular coordinate system. Results show that the profile image almost clings to the actual profile of the defect and the average profile error is only 4.3%. The proposed guided wave scattering model and profile imaging method are verified to be able to describe the profile of an actual defect in steel plate with high precision

Defect detection and identification of point-focusing shear-horizontal EMAT for plate inspection

As a kind of nondestructive testing (NDT) method, shear-horizontal (SH)-guided wave detection technology is widely used on an electromagnetic acoustic transducer (EMAT). Although ultrasonic-guided waves perform well in defect location, it is difficult to obtain detailed information about defects, and the low efficiency of EMAT energy conversion still reduces the EMAT’s performance. Therefore, in this work, the defect detection method of different shapes and sizes by point-focusing shear-horizontal (PFSH)-guided wave EMAT with the use of periodic permanent magnet (PPM) is investigated through simulation and experiment. For the purpose of defect classification and quantification, the extraction principles of defect features are obtained through simulation based on the circumferential scatter diagrams, and the neural network (NN) is used to process the features extracted from the experimental data. The results show that by extracting effective defect features from the scatter diagram, high-accuracy classification and high-precision quantification of defects under the influence of the focusing transducer can be achieved